Various types of pumping units have been utilized to pump oil from the ground by vertically reciprocating a polished rod which lifts a rod string and actuates a downhole pump. Typically a walking beam is powered about its center with one end connected to the polished rod and the second end having a counterweight. However, the load presented to the prime mover in actuating the walking beam is cyclic and is not constant.
The present invention overcomes the disadvantages of the prior art pumping units by providing a hydraulic pumping unit having a linear counterbalance and allows the power requirements to be substantially constant throughout the pumping stroke. In addition, a hydraulic and electrical control circuit provides reliable control and actuation of the pumping unit.